This invention relates generally to a printing system and, more particularly, to a halftone pattern enhancement system which substitutes a second halftone pattern for a first halftone pattern in response to a determination that the image quality of an image corresponding with first halftone pattern will not exceed a preselected image quality threshold.
Personal computers have become commonplace on the desks of most office workers. Typically, much of the work product of such computers is intended to be transformed into hardcopy via a printer using digital imaging technology. A typical printer configuration for this purpose comprises a dedicated printer coupled to the personal computer ("PC"). However, printers used for this purpose are typically small laser printers which have limited functions and features such as a limited tray capacity which restricts the number and types of copy sheets that can be used to make prints on, or which do not have a finishing capability, etc.
On the other hand, larger high speed laser printers normally have a great deal of finishing and copy sheet capability which would allow the PC user to have, for example, custom printing and finishing of his work product, an option which for many PC users would be highly desirable. In practice, the PCs can be used advantageously with a network printing system of the type combining a number of client inputs, such as the PCs, or the like, and one or more printer outputs. In one example of such network printing systems, a client at one of the inputs sends electronic documents that comprise a job over a local area network (LAN) to one of the printers selected for printing of the job. In particular, LANs provide a means by which users running dedicated processors are able to share resources such as printers, file servers and scanners. Integration of shared resources has been a problem addressed by LAN managers. LAN managers have made different network protocols transparent to devices running different network protocols LANs also have a variety of print drivers emitting different page description languages (PDLs), which are directed to specific print devices.
Examples of some recent patents relating to network environments of plural remote terminal shared users of networked printers include Xerox Corporation U.S. Pat. Nos. 5,483,653, 5,243,518, 5,226,112, 5,170,340 and 5,287,194. Some patents on this subject by others include U. S. Pat. Nos. 5,113,355, 5,113,494(originally filed Feb. 27, 1987), 5,181,162, 5,220,674, 5,247,670; 4,953,080 and 4,821,107. Further by way of background, some of the following Xerox.RTM. Corporation U.S. patents also include examples of networked systems with printers: U.S. Pat. Nos. 5,153,577; 5,113,517; 5,072,412; 5,065,347; 5,008,853; 4,947,345; 4,939,507; 4,937,036; 4,920,481; 4,914,586; 4,899,136; 4,453,128; 4,063,220; 4,099,024; 3,958,088; 3,920,895; and 3,597,071. Also noted are IBM Corp. U.S. Pat. Nos. 4,651,278 and 4,623,244, as well as Canon U.S. Pat. No. 4,760,458 and Jap. Pub. No. 59-63872 published Nov. 4, 1984. Some of these various above patents also disclose multi-functional printing systems.
Some other network system related publications include "Xerox Office Systems Technology" "Xerox 8000 Series Products: Workstations, Services, Ethernet, and Software Development" .COPYRGT.1982, 1984 by Xerox Corporation, OSD-R8203A, Ed. T. Linden and E. Harslem, with a "Table of Contents" citing its numerous prior publications sources, and an Abstract noting the April 1981 announcement of "the 8110 Star Information System, A New Personal Computer . . . "; "Xerox System Integration Standard Printing Protocol XSIS 118404", April 1984; "Xerox Integrated Production Publishers Solutions: " Booklet No. "610P50807" "11/85"; "Printing Protocol-Xerox System Integration Standard" .COPYRGT.1990 by Xerox Corporation, XNSS 119005 May 1990; "Xerox Network Systems Architecture", "General Information Manual", XNSG 068504 April 1985, with an extensive annotated bibliography, .COPYRGT.1985 by Xerox Corporation; "Interpress: The Source Book", Simon & Schuster, Inc., New York, N.Y., 1988, by Harrington, S. J. and Buckley, R. R.; Adobe Systems Incorporated "PostScript" Language Reference Manual", Addison-Wesley Co., 1990; "Mastering Novell Netware.RTM.", 1990, SYBEX, Inc., Alameda, Calif., by Cheryl E. Currid and Craig A. Gillett; "Palladium Print System" .COPYRGT.MIT 1984, et sec; "Athena85" "Computing in Higher Education: The Athena Experience", E. Balkovich, et al, Communications of the ACM, 28(11) pp. 1214-1224, November, 1985; and "Apollo87 The Network Computing Architecture and System: An Environment for Developing Distributed Applications", T. H. Dineen, et al, Usenix Conference Proceedings, June 1987.
Noted regarding commercial network systems with printers and software therefor is the 1992 Xerox Corporation "Network Publisher" version of the 1990"DocuTech.RTM." publishing system, including the "Network Server" to customer's Novell.RTM. 3.11 networks, supporting various different network protocols and "Ethernet"; and the Interpress Electronic Printing Standard, Version 3.0, Xerox System Integration Standard XNSS 048601 (January 1986). Also, the much earlier Xerox Corporation "9700 Electronic printing System"; the "VP Local Laser Printing" software application package, which, together with the Xerox "4045" or other Laser Copier/Printer, the "6085" "Professional Computer System" using Xerox Corporation "ViewPoint" or "GlobalView.RTM." software and a "local printer print service! Option" kit, comprises the "Documenter" system. The even earlier Xerox Corporation "8000" "Xerox Network Services Product Descriptions" further describe other earlier Xerox Corporation electronic document printing systems. Eastman Kodak "LionHeart.RTM." systems, first announced Sept. 13, 1990, are also noted.
Current popular commercial published "systems software" with LAN workstation connections include Novell DOS 7.0, "Windows.RTM." NT 3.1, and IBM OS/2 Version 2.1.
Disclosures of all of the patents cited above are incorporated herein by reference.
Commonly, a PDL transmitted across a network from a client to a target printer includes one or more bitmaps representing a halftone pattern. In a typical network printing context, it has been found that the image quality of each halftone pattern rendered at the target printer will vary as a function of either the degree to which the target printer handles incoming halftone patterns or the manner in which each halftone pattern is generated at the client. In particular, with respect to known PostScript applications, handling of halftones is optimized since the default halftone designed for the printer is used. On the other hand, problems can arise with respect to those applications in which a printer specific halftone in the print driver is ignored and, instead, a set of halftones which ignores the particular marking capability of the target printer is generated.
For example, a typical PCL application generates a set of halftones suitable for use on a "write black" printer while certain PCL capable printers incorporate "write white" technology. It has been found that halftone image quality can, to a significant degree, be dependent on whether the printer is write white or write black. Accordingly, when a job with one or more halftones, generated with a PCL application, is provided to a write white printer, image degradation may result in marking unless certain selected image processing (e.g. bit adding, shifting, overstriking and/or ORing) is performed on the one or more halftones. An example of image processing useful in compensating for image quality degradation resulting from the interpretation of a PCL generated job at a white write printer can be found in U.S. Pat. No. 5,410,615 to Mailloux.
While image processing of the type found in '615 Patent may represent one viable solution to alleviating, such image processing can be less than desirable since it can represent added cost and may, under certain circumstances, not even provide the level of image quality demanded by the customer. Additionally, image processing of a halftone pattern may require a level of both processing and memory overhead that is undesirable. It would be desirable to provide a simple and economic technique which facilitates the printing of a job on a printer which is at least partially unsuitable for generating halftones in the job due to either the manner in which the job was orginally created or certain constraints of the printer upon which the job is to executed.